Delivery of drugs or therapeutics to bones is an often desirable but difficult to achieve process, especially if one desire to focus the delivery to the interior of a bone or to a particular area in a bone.
US 2014/0236242 teaches to use a screw for bone fixation comprising an elongate shank defining an internal longitudinal passage and at least one shank aperture in communication with the internal longitudinal passage. However with such device, the discharge of substances within the bone is mainly distal due to the distal opening required to insert a guiding wire. Such guiding wire is necessary for minimally invasive surgery. Minimally invasive surgery, which is applied to an increasing number of cases, required indeed guiding wires to position an implant to the implantation site.
EP 2570093 suggests inserting a plug member into the internal longitudinal passage to close the passage at the distal end after removal of the guiding wire. Such system enables radial ejection of substance by preventing distal discharge of fluid. However, insertion of the plug member required complex handling.
It is thus a first object of the invention to provide a bone screw enabling discharge of substances in an oriented manner while allowing minimally invasive surgery.
The object is solved by the device as defined in the claims. The present invention especially provides a bone screw having a longitudinal axis, a through bore extending coaxially and at least three blind channels angularly-disposed around the through bore. Each blind channel is connected to the exterior of the bone screw by fenestrations. With such device, the discharge of substances may be oriented by selecting the desired blind channel.
Orienting the delivery of substance within the bone may be of importance, especially for treating the intervertebral disc. Intervertebral disc has indeed no specific vascularization. Avascular tissue nutrients are delivered by diffusion from the capillaries at the disc-vertebral body interface. Consequently, intravenous treatments have difficulties to access intervertebral disc. The state of the art procedure requires disc puncture and perforation of the disc annulus. However, such procedure often leads to degenerative disc disease.
It is consequently a second object of the invention to enable treatment of the intervertebral disc without puncture of the disc annulus.
The cannulated bone screw according to the invention has the advantage that it can deliver substance inside the vertebral body precisely towards the superior or inferior end plate; such substances being subsequently diffused inside respectively the superior or inferior intervertebral disc.
Alternatively, the cannulated bone screw according to the invention may also be used with radioactive needles positioned in the blind channels, thereby providing local radiotherapy within the bone.
After the implant is inserted into the vertebral body, a catheter, inserted in a blind channel, may be connected to a pump implanted just below the surface of the skin. The patient may thereby keep the system for several hours to several days. Once the treatment is achieved, in order to access the bone screw percutaneously, it is necessary that extracting means locate the head screw easily.
It is thus a third object of the invention to provide a bone screw enabling removal by minimally invasive surgery.
The object is solved by the device as defined in the claims. In particular, the present invention provides flexible directing means secured to the screw head such that extracting means may be guided to the screw head. As the directing means are secured to the screw head, the extracting means may slide around said directing means until it abuts against the screw head for retrieval.